U.S. patent application number 10/935266 was filed with the patent office on 2005-03-24 for resin composition, prepreg, laminate sheet and printed wiring board using the same and method for production thereof.
This patent application is currently assigned to Hitachi Chemical Company, Ltd.. Invention is credited to Amou, Satoru, Minami, Nobuyuki, Nagai, Akira, Nakamura, Yoshihiro, Umino, Morimichi.
Application Number | 20050064159 10/935266 |
Document ID | / |
Family ID | 34191380 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050064159 |
Kind Code |
A1 |
Amou, Satoru ; et
al. |
March 24, 2005 |
Resin composition, prepreg, laminate sheet and printed wiring board
using the same and method for production thereof
Abstract
There are provided a resin composition comprising a crosslinking
component with a weight average molecular weight of 1,000 or less
having a plurality of styrene groups and represented by the
following formula: 1 wherein R is a hydrocarbon skeleton, each of
R.sup.1s is a hydrogen atom or a hydrocarbon group, each of
R.sup.2, R.sup.3 and R.sup.4 is a hydrogen atom or an alkyl group,
m is an integer of 1 to 4, and n is an integer of 2 or more, at
least one high-molecular weight compound, an inorganic filler, and
at least one treating agent for said inorganic filler; its cured
product; and a prepreg, a laminate sheet having a conductor layer,
and a multilayer printed wiring board obtained by processing the
conductor layer of the laminate sheet into wiring.
Inventors: |
Amou, Satoru; (Hitachi,
JP) ; Umino, Morimichi; (Hitachiota, JP) ;
Nagai, Akira; (Hitachi, JP) ; Nakamura,
Yoshihiro; (Shimodate, JP) ; Minami, Nobuyuki;
(Shimodate, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-9889
US
|
Assignee: |
Hitachi Chemical Company,
Ltd.
Tokyo
JP
|
Family ID: |
34191380 |
Appl. No.: |
10/935266 |
Filed: |
September 8, 2004 |
Current U.S.
Class: |
428/209 ;
428/626 |
Current CPC
Class: |
Y10T 428/24995 20150401;
Y10T 428/31645 20150401; H05K 1/024 20130101; Y10T 428/24917
20150115; H05K 2201/0158 20130101; H05K 2201/0239 20130101; H05K
2201/0209 20130101; Y10T 428/24994 20150401; Y10T 428/12569
20150115; H05K 2201/012 20130101; Y10T 428/249951 20150401; H05K
3/4626 20130101; Y10T 428/249952 20150401; H05K 1/032 20130101 |
Class at
Publication: |
428/209 ;
428/626 |
International
Class: |
B32B 015/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2003 |
JP |
2003-327970 |
Claims
1. A resin composition comprising: a crosslinking component with a
weight average molecular weight of 1,000 or less having a plurality
of styrene groups and represented by the following general formula:
6 wherein R is a hydrocarbon skeleton; each of R.sup.1s, which may
be the same or different, is a hydrogen atom or a hydrocarbon group
of 1 to 20 carbon atoms; each of R.sup.2, R.sup.3 and R.sup.4,
which may be the same or different, is a hydrogen atom or an alkyl
group of 1 to 6 carbon atoms; m is an integer of 1 to 4; and n is
an integer of 2 or more, at least one high-molecular weight
compound with a weight average molecular weight of 5,000 or more,
an inorganic filler having a dielectric loss tangent of 0.002 or
less, and at least one treating agent.
2. The resin composition according to claim 1, wherein said
treating agent is supported near the surface of said inorganic
filler.
3. The resin composition according to claim 1, characterized by
containing, as said at least one treating agent, at least one
reactive treating agent having a functional group chemically
bondable to the polyfunctional styrene compound.
4. The resin composition according to claim 1, wherein said
inorganic filler has an average particle size of 0.5 to 60
.mu.m.
5. The resin composition according to claim 1, wherein said at
least one high-molecular weight compound is at least one resin
selected from the group consisting of polymers comprising repeating
units derived from at least one of butadiene, isoprene, styrene,
methylstyrene, ethylstyrene, divinylbenzene, acrylic esters,
acrylonitrile, N-phenylmaleimide and N-vinylphenylmaleimide;
substituted or unsubstituted polyphenylene oxides; and polyolefins
having an alicyclic structure.
6. The resin composition according to claim 1, which further
comprises at least one flame retardant represented by the following
general formulas: 7
7. A prepreg comprising a dried glass cloth or glass nonwoven
fabric impregnated with a resin composition comprising: a
crosslinking component with a weight average molecular weight of
1,000 or less having a plurality of styrene groups and represented
by the following general formula: 8 wherein R is a hydrocarbon
skeleton; each of R.sup.1s, which may be the same or different, is
a hydrogen atom or a hydrocarbon group of 1 to 20 carbon atoms;
each of R.sup.2, R.sup.3 and R.sup.4, which may be the same or
different, is a hydrogen atom or an alkyl group of 1 to 6 carbon
atoms; m is an integer of 1 to 4; and n is an integer of 2 or more,
at least one high-molecular weight compound with a weight average
molecular weight of 5,000 or more, an inorganic filler having a
dielectric loss tangent of 0.002 or less, and at least one treating
agent.
8. The prepreg according to claim 7, wherein said glass cloth or
glass nonwoven fabric has been surface-treated with at least one
treating agent.
9. The prepreg according to claim 7, characterized by comprising at
least one reactive treating agent having a functional group
chemically bondable to the polyfunctional styrene compound.
10. The prepreg according to claim 7, wherein said glass cloth or
glass nonwoven fabric has a dielectric loss tangent of 0.002 or
less.
11. A laminate sheet having a conductor layer on one or both sides
of a cured product of a prepreg comprising a dried glass cloth or
glass nonwoven fabric impregnated with a resin composition
comprising: a crosslinking component with a weight average
molecular weight of 1,000 or less having a plurality of styrene
groups and represented by the following general formula: 9 wherein
R is a hydrocarbon skeleton; each of R.sup.1s, which may be the
same or different, is a hydrogen atom or a hydrocarbon group of 1
to 20 carbon atoms; each of R.sup.2, R.sup.3 and R.sup.4, which may
be the same or different, is a hydrogen atom or an alkyl group of 1
to 6 carbon atoms; m is an integer of 1 to 4; and n is an integer
of 2 or more, at least one high-molecular weight compound with a
weight average molecular weight of 5,000 or more, an inorganic
filler having a dielectric loss tangent of 0.002 or less, and at
least one treating agent.
12. The laminate sheet according to claim 11, wherein a surface of
said conductor layer in contact with the prepreg has been treated
with a treating agent.
13. The laminate sheet according to claim 12, which contains, as
said at least one treating agent, at least one reactive treating
agent having a functional group chemically bondable to the
polyfunctional styrene compound.
14. A multilayer printed wiring board comprising laminate sheets
having a conductor layer on one or both sides of a cured product of
a prepreg comprising a dried glass cloth or glass nonwoven fabric
impregnated with a resin composition comprising: a crosslinking
component with a weight average molecular weight of 1,000 or less
having a plurality of styrene groups and represented by the
following general formula: 10 wherein R is a hydrocarbon skeleton;
each of R.sup.1s, which may be the same or different, is a hydrogen
atom or a hydrocarbon group of 1 to 20 carbon atoms; each of
R.sup.2, R.sup.3 and R.sup.4, which may be the same or different,
is a hydrogen atom or an alkyl group of 1 to 6 carbon atoms; m is
an integer of 1 to 4; and n is an integer of 2 or more, at least
one high-molecular weight compound with a weight average molecular
weight of 5,000 or more, an inorganic filler having a dielectric
loss tangent of 0.002 or less, and at least one treating agent,
said conductor layer having been processed to form wiring, said
prepreg having been inserted between the laminate sheets so that
the laminate sheets adhere to one another.
15. A resin-layer-provided conductor foil made from a resin
composition as claimed in claim 1 which contains, as said at least
one treating agent, at least one reactive treating agent having a
functional group chemically bondable to the polyfunctional styrene
compound.
16. A multilayer printed wiring board comprising a laminate sheet
having a conductor layer on a surface, the conductor layer having
been processed to form wiring, and a resin-layer-provided conductor
foil as claimed in claim 15 adhered on the laminate sheet, an outer
layer of the conductor foil having been processed to form
wiring.
17. A multilayer printed wiring board comprising a laminate sheet
having a first conductor layer on a surface, the first conductor
layer having been processed to form wiring, a resin composition as
claimed in claim 1 on the surface of said laminate sheet carrying
the wiring, the composition having been dried and optionally cured
and a second conductor layer formed on an outer layer, the second
conductor layer having been processed to form wiring.
Description
[0001] The present application claims priority from Japanese
application JP 2003-327970 filed on 19 Sep. 2003, the content of
which is hereby incorporated by reference into this
application.
TECHNICAL FIELD
[0002] The present invention relates to a multilayer printed wiring
board, a conductor-provided laminate sheet, a prepreg and a
resin-layer-provided conductor foil which are sufficiently low in
dielectric loss to be suitable for high-frequency signals, and a
resin composition with a low dielectric loss tangent property used
for producing them, its cured product, prepreg, laminate sheet and
a multilayer printed wiring board and the like.
BACKGROUND ART
[0003] In recent years, the signal frequency region for information
and communication apparatus (e.g., PHS and mobile phones) and the
CPU clock time of computers reach the GHz region and employment of
a higher frequency has been in progress. The transmission loss of
an electric signal is expressed as the sum of dielectric loss,
conductor loss and radiation loss, and the dielectric loss,
conductor loss and radiation loss increase with an increase of the
frequency of the electric signal. Since the transmission loss
decays the electric signal to deteriorate the reliability of the
electric signal, a wiring board for high-frequency signals should
be designed to suppress the increase of the dielectric loss,
conductor loss and radiation loss. The dielectric loss is
proportional to the product of the square root of the relative
permittivity of an insulator forming a circuit, the dielectric loss
tangent of the insulator and the frequency of signals used.
Therefore, the increase of the dielectric loss can be suppressed by
choosing an insulating material having a low permittivity and a low
dielectric loss tangent, as the insulator.
[0004] Typical materials having a low permittivity and a low
dielectric loss tangent are described below. Fluororesins
represented by polytetrafluoroethylenes (PTFE) have both a low
permittivity and a low dielectric loss tangent and hence have been
used as a material for a substrate suitable for high-frequency
signals since early times. On the other hand, various insulating
materials containing no fluorine and having a low permittivity and
a low dielectric loss tangent have been investigated which are easy
to make into a varnish by the use of an organic solvent, have a low
molding temperature and a low curing temperature, and are easy to
handle.
[0005] JP-A-2002-249531, JP-A-2003-12710 and JP-A-2003-105036
disclose examples of employment of a polyfunctional styrene
compound as a crosslinking component. In addition, in many of these
examples, permittivity adjustment, flame retardation and strength
improvement by the addition of an inorganic filler are
described.
[0006] It is generally known that the conductor loss and the
radiation loss can be reduced by forming a conductor wiring with a
low surface roughness by the use of a metal having a low conductor
resistance, such as gold, silver, copper or the like.
[0007] The cured products of resin compositions and prepregs
disclosed in JP-A-2002-249531, JP-A-2003-12710 and JP-A-2003-105036
are materials having a low permittivity but have a dielectric loss
tangent of more than 0.002. Thus, they are still unsatisfactory as
an insulating material in their recent application at a high
frequency. The present inventor investigated a method for further
reducing the dielectric loss tangent of the cured products of resin
compositions and prepregs, and consequently found that the
dielectric loss tangent (dielectric loss) of the cured products
could be reduced by adding a specific treating agent to the resin
compositions or previously treating an inorganic filler, a base
material (e.g., glass cloth), copper foil or the like.
[0008] Accordingly, an object of the present invention is to reduce
the dielectric loss tangent of a cured product of a resin
composition containing a crosslinking component having a plurality
of styrene groups, a high-molecular weight compound and an
inorganic filler.
[0009] Another object of the present invention is to provide a
resin composition having both an excellent flame retardancy like
that of the above-mentioned resin composition and a very low
dielectric loss tangent and further provide a printed wiring board,
a laminate sheet, a prepreg and a resin-layer-provided conductor
foil which are obtained by using the resin composition.
SUMMARY OF THE INVENTION
[0010] The present invention includes, at least, the following
items.
[0011] (1) A resin composition comprising:
[0012] a crosslinking component with a weight average molecular
weight of 1,000 or less having a plurality of styrene groups and
represented by the following general formula: 2
[0013] wherein R is a hydrocarbon skeleton; each of R.sup.1s, which
may be the same or different, is a hydrogen atom or a hydrocarbon
group of 1 to 20 carbon atoms; each of R.sup.2, R.sup.3 and
R.sup.4, which may be the same or different, is a hydrogen atom or
an alkyl group of 1 to 6 carbon atoms; m is an integer of 1 to 4;
and n is an integer of 2 or more,
[0014] at least one high-molecular weight compound with a weight
average molecular weight of 5,000 or more, and
[0015] an inorganic filler having a dielectric loss tangent of
0.002 or less,
[0016] said resin composition further comprising at least one
treating agent for said inorganic filler.
[0017] (2) The composition according to the item (1), wherein said
treating agent(s) is supported on the surface of the inorganic
filler.
[0018] (3) The composition according to the item (1) or (2), which
contains, as said at least one treating agent, at least one
reactive treating agent having a functional group chemically
bondable to the polyfunctional styrene compound.
[0019] (4) The composition according to any one of the items (1) to
(3), wherein the average particle size of said inorganic filler
ranges 0.5 to 60 .mu.m.
[0020] (5) The composition according to any one of the items (1) to
(4), wherein said at least one high-molecular weight compound is at
least one resin selected from the group consisting of polymers
comprising repeating units derived from at least one of butadiene,
isoprene, styrene, methylstyrene, ethylstyrene, divinylbenzene,
acrylic esters, acrylonitrile, N-phenylmaleimide and
N-vinylphenyl-maleimide; substituted or unsubstituted polyphenylene
oxides; and polyolefins having an alicyclic structure.
[0021] (6) The composition according to any one of the items (1) to
(5), which further comprises at least one of a curing catalyst
capable of polymerizing styrene groups and a polymerization
inhibitor capable of suppressing the polymerization of styrene
groups.
[0022] (7) The composition according to any one of the items (1) to
(6), which further comprises at least one flame retardant.
[0023] (8) The composition according to the item (7), which
comprises at least one at least one flame retardant having a
dielectric loss tangent of 0.002 or less, as the above-mentioned at
least one flame retardant.
[0024] (9) The composition according to the item (7) or (8), which
comprises at least one flame retardant represented by the following
general formulas, as the above-mentioned at least one flame
retardant: 3
[0025] (10) A cured product of a composition according to any one
of the above items (1) to (9).
[0026] (11) A prepreg obtained by impregnating glass cloth or glass
nonwoven fabric with a composition according to any one of the
above items (1) to (9), and drying the composition.
[0027] (12) The prepreg according to the item (11), wherein said
glass cloth or glass nonwoven fabric has been subjected to surface
treatment with at least one treating agent.
[0028] (13) The prepreg according to the item (12), characterized
by containing at least one reactive treating agent having a
functional group chemically bondable to the polyfunctional styrene
compound, as said at least one treating agent.
[0029] (14) The prepreg according to any one of the items (11) to
(13), wherein the dielectric loss tangent of said glass cloth or
glass nonwoven fabric is 0.002 or less.
[0030] (15) A cured product of a prepreg according to any one of
the above items (11) to (14).
[0031] (16) A laminate sheet obtained by providing a conductor
layer on one or both sides of a cured product of a prepreg
according to the above item (15).
[0032] (17) The laminate sheet according to the item (16), wherein
the average of surface roughness values at 10 points of the surface
of said conductor layer in contact with the prepreg ranges from 1
to 3 .mu.m.
[0033] (18) The laminate sheet according to the item (17), wherein
the surface of said conductor layer in contact with the prepreg has
been treated with a treating agent.
[0034] (19) The laminate sheet according to the item (18), which
contains at least one reactive treating agent having a functional
group chemically bondable to the polyfunctional styrene compound,
as said at least one treating agent.
[0035] (20) A multilayer printed wiring board obtained by
processing the conductor layer of a laminate sheet according to any
one of the above items (16) to (19) into wiring, laminating such
laminate sheets with prepregs inserted between the laminate sheets
so as to alternate with them, and then adhering the laminate sheets
to one another.
[0036] (21) A resin-layer-provided conductor foil obtained by
applying a resin composition according to any one of the above
items (1) to (9) on one side of conductor foil and then drying the
composition.
[0037] (22) The resin-layer-provided conductor foil according to
the item (21), wherein the average of surface roughness values at
10 points of the surface of said conductor foil in contact with the
resin layer is 1 to 3 .mu.m.
[0038] (23) The resin-layer-provided conductor foil according to
the item (22), wherein the surface of said conductor foil in
contact with the resin layer has been treated with a treating
agent.
[0039] (24) The resin-layer-provided conductor foil according to
the item (23), which contains at least one reactive treating agent
having a functional group chemically bondable to the polyfunctional
styrene compound, as said at least one treating agent.
[0040] (25) A laminate sheet obtained by attaching second conductor
foil to a resin-layer-provided conductor foil according to any one
of the above items (21) to (24) through the resin layer of the
resin-layer-provided conductor foil to laminate the conductor
foils, and adhering them to each other.
[0041] (26) A multilayer printed wiring board obtained by forming
wiring in a laminate sheet having a conductor layer on the surface,
laminating a resin-layer-provided conductor foil according to any
one of the above items (21) to (24) on the laminate sheet, adhering
them to each other, and then processing the conductor foil as outer
layer into wiring.
[0042] (27) A multilayer printed wiring board obtained by forming
wiring in a laminate sheet having a first conductor layer on the
surface, applying a resin composition according to any one of the
above items (1) to (9) on the surface having the wiring formed
thereon, drying the composition, curing the composition if
necessary, forming a second conductor layer as an outer layer, and
then processing the second conductor layer as an outer layer into
wiring.
[0043] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 is a schematic diagram showing a process for
producing a multilayer wiring board in one example.
[0045] FIG. 2 is a schematic diagram showing a process for
producing a multilayer wiring board in another example.
[0046] The symbols have the following meanings.
[0047] 1--copper foil subjected to dielectric loss tangent
reduction treatment, 2--resin substrate, 3--photoresist,
4--prepreg, 5--inner-layer wiring, 6--outer-layer wiring,
7--through-hole, 8--plating catalyst, 9--seed film, 10--opening,
11--electrode, 12--plated copper film, 13--resin layer.
DETAILED DESCRIPTION OF THE INVENTION
[0048] According to the present invention, a cured product can be
obtained which has a very low dielectric loss tangent, a high glass
transition temperature and an excellent flame retardancy.
[0049] It has been already mentioned that an insulator comprising a
polyfunctional styrene compound as a crosslinking component has a
very low dielectric loss tangent. The polyfunctional styrene
compound can be improved in properties such as mechanical
properties, adhesiveness, film-forming properties and the like by
blending with various high-molecular weight compounds, and can be
given flame retardancy by the addition of a flame retardant. Many
blending polymers and flame retardants, however, have a higher
dielectric loss tangent in some cases than does a cured product of
the polyfunctional styrene compound. Therefore, the low dielectric
loss tangent due to the polyfunctional styrene compound was often
increased in a cured product of a resin composition that was tried
to be improved in mechanical properties, adhesiveness, film-forming
properties and flame retardancy by polymer blending and the
addition of a flame retardant.
[0050] As to a method for suppressing the increase of the
dielectric loss tangent, the addition of an inorganic filler having
a very small dielectric loss tangent value and the relationship
between the structure of a flame retardant and its dielectric loss
tangent were investigated. Consequently, it was found that in the
case of a resin composition whose dielectric loss tangent after
curing is 0.002 or less, the dielectric loss tangent of a cured
product of the composition is often not reducible by mere addition
of an inorganic filler having a low dielectric loss tangent to a
resin system. As causes for this problem, there are conjectured
peeling of the resin and the inorganic filler from each other at
the boundary surface between them and the adsorption of a slight
amount of impurities (e.g., water) on the peeled portions which
accompanies the peeling.
[0051] The problem will be solvable by modifying the surface of the
inorganic filler with a specific treating agent to increase its
adhesion to the resin. It was also found that the dielectric loss
tangent of a flame retardant having a specific structure is very
low and that the dielectric loss tangent of a resin composition
containing the flame retardant is also very low. Thus, also when no
polyolefin is used as a blending polymer, a resin composition can
be obtained which have not only a very low dielectric loss tangent
but also flame retardancy. Moreover, it was found that also in the
case of a cured product of a prepreg obtained by impregnating glass
cloth or glass nonwoven fabric with this composition and drying and
then curing the composition, the dielectric loss tangent of the
cured product is reduced when the surface of the glass cloth or
glass nonwoven fabric is treated with a treating agent.
[0052] The term "treating agent" used in the present specification
means a substance capable of reducing the dielectric loss tangent
of a cured product of, for example, a resin composition or a
prepreg, which comprises a polyfunctional styrene compound as
crosslinking agent, at least one high-molecular weight compound
having a weight average molecular weight of 5,000 or more and an
inorganic filler having a dielectric loss tangent of 0.002 or less.
The treating agent has a group reactive to the above-mentioned
polyfunctional styrene compound or has a group adsorbable on and
bondable to the inorganic filler.
[0053] Furthermore, it was found that dielectric loss tangent
reduction treatment of conductor foil having an excellent
transmission characteristic for high-frequency signals and a low
surface roughness increases the adhesion between a cured product of
the composition of the present invention and the conductor foil. On
the basis of these findings, there have been obtained a printed
wiring board suitable for high-frequency signals and a laminate
sheet, a prepreg, a resin-layer-provided conductor foil and a resin
composition which are components of the printed wiring board.
[0054] The resin composition of the present invention and its cured
product are explained below. The resin composition of the present
invention is a resin composition comprising a crosslinking
component with a weight average molecular weight of 1,000 or less
having a plurality of styrene groups and represented by the
following general formula: 4
[0055] wherein R is a hydrocarbon skeleton; each of R.sup.1s, which
may be the same or different, is a hydrogen atom or a hydrocarbon
group of 1 to 20 carbon atoms; each of R.sup.2, R.sup.3 and
R.sup.4, which may be the same or different, is a hydrogen atom or
an alkyl group of 1 to 6 carbon atoms; m is an integer of 1 to 4;
and n is an integer of 2 or more, at least one high-molecular
weight compound with a weight average molecular weight of 5,000 or
more, an inorganic filler having a dielectric loss tangent of 0.002
or less, and at least one treating agent. In the present
specification, the weight average molecular weight refers to a
weight average molecular weight in terms of styrene measured by gel
permeation chromatography (GPC).
[0056] During the preparation of a varnish from the resin
composition, the above-mentioned inorganic filler reacts with the
treating agent(s) or a layer of the treating agent(s) is formed on
the surface of the filler. Since the inorganic filler whose surface
has been modified with the treating agent(s) is excellent in
adhesion to the resin, there are prevented peeling of the resin and
the inorganic filler from each other at the boundary surface
between them and the intrusion of impurities into the peeled
portions which accompanies the peeling. Therefore, the inorganic
filler is very effective in reducing the dielectric loss tangent of
a cured product of the resin composition. The same effect as above
can be obtained also by incorporating the above-mentioned treating
agent(s) into the resin composition after previously supporting the
treating ageht(s) on the inorganic filler.
[0057] The inorganic filler to be added is preferably an inorganic
filler having a dielectric loss tangent lower than that of a cured
product of the same resin composition as above except for
containing no inorganic filler. The value of the dielectric loss
tangent of the inorganic filler is preferably as low as possible.
Specifically, the value of the dielectric loss tangent of the
inorganic filler at a signal frequency used in a printed wiring
board is lower than that of a cured product of the resin
composition containing no filler and is 0.002 or less, preferably
0.001 or less.
[0058] Such an inorganic filler can be selected from, for example,
various ceramics such as well-known titanium-barium-neodymium
series ceramics, titanium-barium-tin series ceramics, zinc-calcium
series ceramics, titanium dioxide series ceramics, barium titanate
series ceramics, lead titanate series ceramics, strontium titanate
series ceramics, calcium titanate series ceramics, bismuth titanate
series ceramics, magnesium titanate series ceramics, zirconium
titanate series ceramics, zinc titanate series ceramics, strontium
zirconate series ceramics, CaWO.sub.4 series ceramics,
Ba(Mg,Nb)O.sub.3 series ceramics, Ba(Mg,Ta)O.sub.3 series ceramics,
Ba(Co,Mg,Nb)O.sub.3 series ceramics, Ba(Co,Mg,Ta)O.sub.3 series
ceramics, Ba(Zn,Nb)O.sub.3 series ceramics, Ba(Zn,Ta)O.sub.3 series
ceramics and the like; and various glasses such as silicon dioxide,
SiO.sub.2--CaO--Al.sub.2O.sub.3--B.sub.2O.sub.3--MgO-K.sub.2O--N-
a.sub.2O glass (E-glass),
SiO.sub.2--Al.sub.2O.sub.3--MgO-K.sub.2O--Na.sub- .2O glass
(T-glass), SiO.sub.2--Al.sub.2O.sub.3--B.sub.2O.sub.3--K.sub.2O--
-Na.sub.2O glass (D-glass),
SiO.sub.2--CaO--Al.sub.2O.sub.3--B.sub.2O.sub.-
3--MgO-K.sub.2O--Na.sub.2O--TiO.sub.2 glass (NE-glass) and the
like.
[0059] These inorganic fillers may be used singly or as a composite
thereof depending on their purpose such as permittivity adjustment,
and may be used in the form of a balloon, a porous material,
needles, a sphere or a shell having a resin phase in its
center.
[0060] The particle size of the inorganic filler preferably
incorporated into the resin composition of the present invention
must necessarily be smaller than the thickness of the prepreg, the
laminate sheet and the resin layer of the resin-layer-provided
conductor foil from the viewpoint of reliability on insulation.
Specifically, the major axis of the inorganic filler is 0.5 to 100
.mu.m on an average, preferably 0.5 to 60 .mu.m on an average, more
preferably 0.5 to 30 .mu.m on an average.
[0061] The amount of the inorganic filler added in the present
invention ranges preferably from 10 to 65 vol % based on the total
volume of the polyfunctional styrene compound, the high-molecular
weight compound(s) and the inorganic filler from the viewpoint of
film-forming properties and moldability. When the amount is less
than 10 vol %, the dielectric loss tangent is not sufficiently
reduced in some cases. When the amount is more than 65 vol %, the
following problems are caused in some cases when the composition is
made into a prepreg: the film-forming properties are deteriorated,
resulting in an unsatisfactory appearance, or the moldability and
adhesiveness are remarkably deteriorated. For these reasons, the
amount of the inorganic filler added ranges more preferably from 10
to 50 vol %.
[0062] The treating agent(s) usable in the present invention
includes silane type compounds, titanate type compounds,
aluminum-containing compounds and the like. These compounds can be
divided into (1) compounds which can be chemically bonded to the
polyfunctional styrene compound and (2) compounds which are not
chemically reactive to the aforesaid styrene compound but can be
adsorbed on the inorganic filler.
[0063] The compounds of the above-mentioned group (1) include, for
example, dimethylvinylmethoxysilane, methyl-vinyldimethoxysilane,
.gamma.-methacryloxypropyltrimethoxysilane, vinyltrichlorosilane,
vinyltrimethoxysilane, vinyltriethoxy-silane,
p-styryltrimethoxysilane,
3-methacryloxypropyl-methyldimethoxysilane,
3-methacryloxypropyltrimethox- y-silane and
3-acryloxypropyltrimethoxysilane.
[0064] The compounds of the above-mentioned group (2) include, for
example, methyldiethoxysilane, trimethyl-methoxysilane,
dimethylethoxysilane, trimethylethoxysilane,
dimethylvinylethoxysilane, dimethyldiethoxysilane,
methyl-trimethoxysilane, methylvinyldimethoxysila- ne,
tetramethoxy-silane, diphenyldimethoxysilane,
methyltriethoxysilane, phenyltrimethoxysilane, tetraethoxysilane,
phenyltriethoxy-silane, methyldimethoxysilane,
.gamma.-aminopropyltriethoxysilane,
N-(.beta.-aminoethyl)-.gamma.-aminopropyltrimethoxysilane,
.gamma.-glycidoxypropylmethoxysilane and
.gamma.-mercaptoxytri-methoxysil- ane.
[0065] In particular, the treating agents of the group (1) having a
functional group reactive to a styrene group are preferably used.
The above-exemplified treating agents may be used singly or as a
composite thereof. The amount of the treating agent(s) added is
preferably as small as possible so long as the addition of the
inorganic filler is effective in reducing the dielectric loss
tangent, because the residue of the treating agent(s) increases the
dielectric loss tangent. Specifically, the amount of the treating
agent(s) added ranges preferably from 0.01 to 5 parts by weight,
more preferably from 0.01 to 2 parts by weight, per 100 parts by
weight of the sum of the polyfunctional styrene compound, the
high-molecular weight compound(s), the inorganic filler and other
additives (e.g., the flame retardant(s) described hereinafter).
[0066] The polyfunctional styrene compound used in the present
invention is preferably a compound having an overall-hydrocarbon
skeleton having styrene groups or substituted styrene groups. The
dielectric loss tangent of a cured product of the resin composition
can be kept low by forming the crosslinking component by the use of
the overall-hydrocarbon skeleton.
[0067] The preferable polyfunctional styrene compound used in the
present invention is explained below. In the above general formula
representing the polyfunctional styrene compound, the hydrocarbon
skeleton represented by R is not particularly limited so long as it
gives a weight average molecular weight of the crosslinking
component of 1,000 or less. That is, although the hydrocarbon
skeleton represented by R may be properly chosen depending on the
presence of the substituents R.sup.1, R.sup.2, R.sup.3 and R.sup.4
in the styrene group, the sizes of the substituents, and the values
of m and n, the number of carbon atoms of the hydrocarbon skeleton
is generally 1 to 60, preferably 2 to 30. The hydrocarbon skeleton
represented by R may be either straight chain skeleton or a
branched chain skeleton, may contain one or more cyclic structures
(e.g., alicyclic structures and aromatic ring structures), and may
contain an unsaturated bond such as that of vinylene, ethynylene or
the like.
[0068] The hydrocarbon skeleton represented by R includes, for
example, ethylene, trimethylene, tetramethylene,
methyltrimethylene, methyltetramethylene, pentamethylene,
methylpentamethylene, cyclopentylene, cyclohexylene, phenylene,
phenylenediethylene, xylylene and
1-phenylene-3-methylpropenylene.
[0069] In the above formula, the hydrocarbon group represented by
R.sup.1 includes, for example, straight chain or branched chain
alkyl groups of 1 to 20 carbon atoms, preferably 1 to 10 carbon
atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,
isobutyl, s-butyl, pentyl, hexyl, decyl, eicosyl and the like;
straight chain or branched chain alkenyl groups of 2 to 20 carbon
atoms, preferably 2 to 10 carbon atoms, such as vinyl, 1-propenyl,
2-propenyl, 2-methylallyl and the like; and aryl groups such as
phenyl, naphthyl, benzyl, phenethyl, styryl, cinnamyl and the
like.
[0070] In the above formula, a plurality of R.sup.1s are present
because n is an integer of 2 or more. A plurality of R.sup.1s are
present also when m is an integer of 2 to 4. Such R.sup.1s present
in a number of two or more may be the same or different, and their
bonding positions may also be the same or different.
[0071] In the above formula, the alkyl group represented by
R.sup.2, R.sup.3 or R.sup.4 includes straight chain or branched
chain alkyl groups of 1 to 6 carbon atoms, such as methyl, ethyl,
n-propyl, isopropyl, n-butyl, isobutyl, hexyl and the like.
[0072] In the above formula, the substituted or unsubstituted vinyl
group (R.sup.3) (R.sup.4)C.dbd.C(R.sup.2)-- is preferably present
in the position meta or para to R on the benzene ring.
[0073] As the crosslinking component used in the present invention,
a polyfunctional monomer with a weight average molecular weight of
1,000 or less having a plurality of substituted or unsubstituted
styrene groups is preferable. Styrene group is highly reactive and
has very low permittivity and dielectric loss tangent. A
hydrocarbon skeleton is preferably employed as the skeleton of the
crosslinking component from the viewpoint of permittivity and
dielectric loss tangent. Owing to the employment, non-volatility
and flexibility can be imparted to the crosslinking component
without deteriorating the properties of styrene group, i.e., its
low permittivity and low dielectric loss tangent.
[0074] In addition, when the crosslinking component with a weight
average molecular weight of 1,000 or less is chosen, it exhibits
melt fluidity at a relatively low temperature and has a good
solubility in an organic solvent, so that the resin composition
becomes easy to mold and make into a varnish. When the weight
average molecular weight of the crosslinking component is too high,
its melt fluidity is low and crosslinking occurs during molding in
some cases, resulting in unsatisfactory molding. Although the
weight average molecular weight of the crosslinking component is
not limited so long as it is 1,000 or less, it is preferably 200 to
500.
[0075] Preferable specific examples of the crosslinking component
are 1,2-bis(p-vinylphenyl)ethane, 1,2-bis(m-vinylphenyl)ethane,
1-(p-vinylphenyl)-2-(m-vinylphenyl)-ethane,
1,4-bis(p-vinylphenylethyl)be- nzene,
1,4-bis(m-vinylphenylethyl)benzene,
1,3-bis(p-vinylphenylethyl)benz- ene,
1,3-bis(m-vinylphenylethyl)benzene,
1-(p-vinylphenylethyl)-4-(m-vinyl- phenylethyl)benzene,
1-(p-vinylphenylethyl)-3-(m-vinylphenylethyl)benzene, and
divinylbenzene polymers (oligomers) having vinyl groups in their
side chains. These crosslinking components may be used singly or in
combination.
[0076] One of the characteristics of the present invention is to
improve the tack-free properties and the mechanical strength of the
cured product by combining the above-mentioned crosslinking
component and the high-molecular weight compound(s). The
high-molecular weight compound(s) used in the present invention
includes, for example, homopolymers or copolymers of butadiene,
isoprene, styrene, methylstyrene, ethylstyrene, divinylbenzene,
acrylic esters (e.g., methyl acrylate, butyl acrylate and phenyl
acrylate), acrylonitrile, N-phenylmaleimide and
N-vinylphenyl-maleimide; substituted or unsubstituted polyphenylene
oxides; and polyolefins having an alicyclic structure. The
high-molecular weight compound(s) is not limited to them. These
high-molecular weight compounds may be used singly or as a
composite thereof.
[0077] The molecular weight of the above-mentioned high-molecular
weight compound(s) is preferably 5,000 or more from the viewpoint
of tack-free properties and film-forming properties in the
production of a prepreg from the resin composition. It is more
preferably 10,000 to 100,000 from the viewpoint of mechanical
strength. It is still more preferably 15,000 to 60,000 for making
the resin composition into a varnish easily and attaining a
suitable viscosity of the varnish easily.
[0078] In addition, from the viewpoint of the heat resistance of a
laminate sheet obtained by the use of the resin composition, the
high-molecular weight compound(s) preferably has a glass transition
temperature of 170.degree. C. or higher or an elastic modulus at
170.degree. C. of 500 MPa or more. The high-molecular weight
compound(s) more preferably has a glass transition temperature of
170 to 300.degree. C. or an elastic modulus at 170.degree. C. of
500 to 3000 MPa. When the high-molecular weight compound(s) has
curing property, its cured product preferably has a glass
transition temperature of 170.degree. C. or higher or an elastic
modulus at 170.degree. C. of 500 MPa or more. The cured product
more preferably has a glass transition temperature of 170 to
300.degree. C. or an elastic modulus at 170.degree. C. of 500 to
3000 MPa.
[0079] Although the amounts of the crosslinking component and
high-molecular weight compound(s) incorporated into the resin
composition of the present invention are not particularly limited,
the crosslinking component and high-molecular weight compound(s)
are preferably incorporated in proportions of 5 to 95 parts by
weight and 95 to 5 parts by weight, respectively. The proportions
of the crosslinking component and the high-molecular weight
compound(s) are more preferably 50 to 95 parts by weight and 50 to
5 parts by weight, respectively. The proportions of the
crosslinking component and the high-molecular weight compound(s)
are still more preferably 50 to 80 parts by weight and 50 to 20
parts by weight, respectively. The solvent resistance, strength,
film-forming properties, adhesiveness and the like of a cured
product of the resin composition are preferably adjusted in the
above proportion ranges.
[0080] Although the resin composition of the present invention can
be cured by mere heating without adding a curing catalyst, a curing
catalyst capable of polymerizing styrene groups may be added in
order to improve the curing efficiency. Although the amount of the
curing catalyst added is not particularly limited, it is preferably
0.0005 to 10 parts by weight per 100 parts by weight of the sum of
the above-mentioned crosslinking component and high-molecular
weight compound(s) because the residues of the curing catalyst tend
to have undesirable influences on the dielectric characteristics.
The addition of the curing catalyst in the above range accelerates
the polymerization of styrene groups, so that a firm cured product
can be obtained at a low temperature.
[0081] There are given below examples of curing catalyst that
generate a cation or a radical species, which can initiate the
polymerization of styrene groups, on heating or light irradiation.
As cationic-polymerization initiators, there can be exemplified
diallyliodonium salts, triallylsulfonium salts and aliphatic
sulfonium salts, which contain BF.sub.4, PF.sub.6, AsF.sub.6 or
SbF.sub.6 as a counter anion. There can be used commercial products
such as SP-70, 172, CP-66 manufactured by Asahi Denka Co., Ltd.,
CI-2855, 2823 manufactured by Nippon Soda Co., Ltd., SI-100L and
SI-150L manufactured by Sanshin Kagaku Kogyo Co., Ltd.
[0082] As free-radical initiators, there can be exemplified benzoin
type compounds such as benzoin, benzoin methyl and the like;
acetophenone type compounds such as acetophenone,
2,2-dimethoxy-2-phenylacetophenone and the like; thioxanthone type
compounds such as thioxanthone, 2,4-diethylthioxanthone and the
like; bisazide compounds such as 4,4'-diazidochalcone,
2,6-bis(4'-azidobenzal)cyclohexanone, 4,4'-diazidobenzophenone and
the like; azo compounds such as azobisisobutyronitrile,
2,2-azobispropane, m,m'-azoxystyrene, hydrazone and the like; and
organic peroxides such as 2,5-dimethyl-2,5-di(t-butylpe-
roxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, dicumyl
peroxide and the like.
[0083] In particular, the organic peroxides or the bisazide
compounds are preferably added which causes hydrogen abstraction
from a compound having no functional group and can cause
crosslinking between the crosslinking component and the
high-molecular weight compound(s).
[0084] A polymerization inhibitor may be added to the resin
composition of the present invention in order to enhance the
storage stability. The amount of the polymerization inhibitor added
is preferably in such a range that the dielectric characteristics
and the reactivity at the time of curing are not remarkably
deteriorated. The amount is preferably 0.0005 to 5 parts by weight
per 100 parts by weight of the sum of the above-mentioned
crosslinking component and high-molecular weight compound(s). When
the polymerization inhibitor is added in the above range, excessive
crosslinking reaction during storage can be suppressed and no
remarkable hindrance to curing is caused during curing. The
polymerization inhibitor includes, for example, quinones and
aromatic diols, such as hydroquinone, p-benzoquinone, chloranil,
trimethylquinone and 4-t-butylpyrocatechol.
[0085] A flame retardant may be added to the resin composition of
the present invention in order to impart flame retardancy to a
laminate sheet or a multilayer printed wiring board, which is
obtained by the use of the resin composition. The amount of the
flame retardant added is properly chosen depending on the flame
retardancy grade required of the laminate sheet or the multilayer
printed wiring board and the performance characteristics of the
flame retardant. As a flame retardant preferably used in the
present invention, there can be exemplified flame retardants whose
dielectric loss tangent at a signal frequency used in a printed
wiring board obtained by the use of said composition is 0.002 or
less. When the signal frequency is 10 GHz, phosphorus-containing
flame retardants and bromine-containing flame retardants can be
exemplified which have any of the following structures A, B, C and
D. 5
[0086] The resin composition of the present invention can be used
in the form of a prepreg obtained by impregnating glass cloth or
glass nonwoven fabric with the composition and then drying the
composition. In this case, the dielectric loss tangent of a cured
product of the prepreg can be reduced by treating the surface of
the glass cloth or glass nonwoven fabric with at least one treating
agent in the same manner as in the case of the inorganic filler. As
the glass cloth or glass nonwoven fabric, there can be exemplified
glass cloths or glass nonwoven fabrics produced from various
glasses such as silicon dioxide (Q-glass),
SiO.sub.2--CaO--Al.sub.2O.sub.3--B.sub.2O.sub.3--MgO-K.sub.2O--Na.sub.2O
glass (E-glass),
SiO.sub.2--Al.sub.2O.sub.3--MgO-K.sub.2O--Na.sub.2O glass
(T-glass),
SiO.sub.2--Al.sub.2O.sub.3--B.sub.2O.sub.3--K.sub.2O--Na- .sub.2O
glass (D-glass), SiO.sub.2--CaO--Al.sub.2O.sub.3--B.sub.2O.sub.3---
MgO-K.sub.2O--Na.sub.2O--TiO.sub.2 glass (NE-glass) and the
like.
[0087] In the present invention, by producing a prepreg by the use
of glass cloth or glass nonwoven fabric, whose dielectric loss
tangent at a signal frequency used in a multilayer printed wiring
board produced by the use of the prepreg is 0.02 or less, there can
be obtained a further improved effect of reducing the dielectric
loss tangent of the insulating layer of the multilayer printed
wiring board. For example, at a signal frequency of 2 GHz or less,
glass cloth or glass nonwoven fabric of Q-glass, D-glass or
NE-glass is preferably used. At a signal frequency of more than 2
GHz, Q-glass is preferably used.
[0088] The prepreg is produced by immersing cloth or nonwoven
fabric as a substrate in a varnish prepared by the use of the resin
composition, and then drying the cloth or nonwoven fabric.
[0089] Furthermore, the resin composition of the present invention
can be used in the form of a resin-layer-provided conductor foil
(for example, resin clad copper obtained by forming a resin layer
on copper foil) produced by applying the composition on conductor
foil and drying the composition. A multilayer printed wiring board
formed by the use of resin clad copper has an excellent
processability in perforating with a drill or a laser because it
has insulating layers not containing glass cloth or glass nonwoven
fabric. The drying conditions for producing the prepreg or the
resin-layer-provided conductor foil are determined depending on the
resin composition. For example, when toluene is used as a solvent,
the drying is preferably conducted at 80 to 130.degree. C. for
approximately 30 to 90 minutes.
[0090] The prepreg of the present invention makes it possible to
produce a laminate sheet having a conductor layer on each or one of
the surfaces by placing conductor foil such as electrolytic-copper
foil or rolled-copper foil on each or one side of the prepreg, and
pressing the resulting assembly with heating. The
resin-layer-provided conductor foil of the present invention makes
it possible to produce a laminate sheet having a conductor layer on
each side by attaching another conductor foil to the surface of the
resin layer and pressing the resulting assembly with heating.
[0091] As to the preferable shape of the conductor foil used in
these laminate sheets, the thickness of the conductor foil is
preferably approximately 9 to 36 .mu.m from the viewpoint of the
precision of processing such as etching. The roughness of the
surface of the conductor foil adhered to the prepreg or the resin
layer is preferably 1 to 3 .mu.m for reducing conductor loss and
radiation loss. Employment of a conductor layer having a low
surface roughness is preferable because it reduces conductor loss
and radiation loss to reduce the loss of electric signals and hence
does not deteriorate the excellent transmission characteristics of
a multilayer printed wiring board obtained by using a resin having
a low dielectric loss tangent.
[0092] In the present invention, the adhesion between the resin and
conductor foil having a low surface roughness can be improved by
modifying the surface of the conductor foil with at least one
treating agent in the same manner as in the case of the
above-mentioned inorganic filler. The improvement of the
adhesiveness of a conductor layer having a low surface roughness
permits prevention of problems such as peeling of the conductor
layer, disconnection and the like in a production process of a
multilayer printed wiring board involving the etching and the
formation of a multilayer structure, which are described
hereinafter.
[0093] The multilayer printed wiring board of the present invention
is explained below. A first example is an example of the production
of a multilayer printed wiring board by the use of the prepreg of
the present invention. The conductor layer of the laminate sheet of
the present invention is processed into wiring by adopting a
conventional etching method, and a plurality of such laminate
sheets having the wiring formed therein are laminated with the
aforesaid prepregs inserted between laminate sheets so as to
alternate with them, and then are pressed with heating to form a
multilayer structure collectively. Thereafter, a through-hole or a
blind via hole is formed by drilling or laser beam machining, and
interlaminar wiring is formed by plating or with an
electroconductive paste to produce the multilayer printed wiring
board.
[0094] A second example is an example of the production of a
multilayer printed wiring board by the use of resin clad copper.
The resin-layer-provided conductor foil of the present invention is
laminated on and adhered to a laminate sheet having wiring formed
therein, by pressing with heating, after which the conductor layer
as outer layer is processed into wiring. Then, a through-hole or a
blind via hole is formed at the joining portion between the inner
layer wiring and the outer layer wiring by drilling or laser beam
machining, and the inner layer wiring and the outer layer wiring
are connected to each other by plating or with an electroconductive
paste. Thus, the multilayer printed wiring board can be
produced.
[0095] A third example is an example of multilayer printed wiring
board obtained by the use of a resin varnish according to the
present invention. The varnish of the resin composition of the
present invention is applied on a laminate sheet having wiring
formed therein, dried and then cured, after which a conductor layer
is formed as an outer layer by sputtering or plating. Then, the
conductor layer as outer layer is processed into wiring, and a
through-hole or a blind via hole is formed at the joining portion
between the inner layer wiring and the outer layer wiring by
drilling or laser beam machining. The inner layer wiring and the
outer layer wiring are connected to each other by plating or with
an electroconductive paste. Thus, the multilayer printed wiring
board can be produced.
[0096] The present invention includes multilayer printed wiring
boards in which a high-frequency circuit and a low-frequency
circuit are mingled together and only the high-frequency circuit
portion is insulated with a cured product of the composition or
prepreg of the present invention. An example of such a multilayer
printed wiring board is described below. Wiring is formed in a
copper-clad laminate sheet having an insulating layer composed of
glass cloth and an epoxy resin (this laminate sheet is abbreviated
as "glass-epoxy substrate"), and then the resin-layer-provided
copper foil of the present invention is laminated on and adhered to
the glass-epoxy substrate by pressing. Thereafter, the copper foil
as outer layer is processed into wiring to produce the multilayer
printed wiring board. In this case, the inner layer wiring right on
the glass-epoxy substrate can be used as wiring for low-frequency
signals and the outer layer wiring can be used as wiring for
high-frequency signals.
[0097] The thus obtained multilayer printed wiring board have such
excellent high-frequency characteristics that dielectric loss is
low because the dielectric loss tangent of the insulating layer for
insulating the high-frequency circuit is low and that conductor
loss and radiation loss are also low because the conductor layer
having a low surface roughness is processed into each wiring.
EXAMPLES
[0098] The present invention is concretely illustrated with
reference to the following examples and reference examples, which
should not be construed as limiting the scope of the invention.
Reagents and evaluation methods are described below.
[0099] (1) Synthesis of 1,2-bis(vinylphenyl)ethane (BVPE)
[0100] 1,2-Bis(vinylphenyl)ethane (BVPE) was synthesized by the
following well-known process. In a 500-ml three-necked flask was
placed 5.36 g (220 mmol) of granular magnesium for Grignard
reaction (mfd. by Kanto Chemical Co., Ltd.), and the flask was
equipped with a dropping funnel, a nitrogen inlet tube and a septum
cap. In a nitrogen stream, the whole system was desiccated with
heating while stirring the magnesium granules with a stirrer.
[0101] In a syringe was place 300 ml of dried tetrahydrofuran, and
injected into the flask through the septum cap. The resulting
mixture was cooled to -5.degree. C., after which 30.5 g (200 mmol)
of vinylbenzyl chloride (VBC, mfd. by Tokyo Kasei Kogyo Co., Ltd.)
was added dropwise thereto over a period of about 4 hours. After
completion of the dropwise addition, the resulting mixture was
continuously stirred at 0.degree. C. for 20 hours. After completion
of the reaction, the reaction mixture was filtered to remove the
residual magnesium, and the filtrate was concentrated with an
evaporator.
[0102] The concentrated solution was diluted with hexane, washed
once with a 3.6% aqueous hydrochloric acid solution and three times
with pure water, and then desiccated over magnesium sulfate. The
desiccated solution was purified by passage through a short column
of silica gel (Wako Gel C300, mfd. by Wako Pure Chemical
Industries, Ltd.)/hexane, and then dried in a vacuum to obtain
BVPE. The obtained BVPE was a mixture of a m-m form (liquid), a m-p
form (liquid) and a p-p form (crystals), and the yield was 90%. The
structure of the obtained BVPE was investigated by .sup.1H-NMR to
find that the measured values agreed with the values described in
literature (6H-vinyl: .alpha.-2H, 6.7, .beta.-4H, 5.7, 5.2;
8H-aromatic: 7.1.about.7.35; 4H-methylene: 2.9). This BVPE was used
as a crosslinking component.
[0103] (2) Other Reagents
[0104] The following were used as high-molecular weight compounds
and other components.
[0105] High-Molecular Weight Compounds;
[0106] PPE: poly-2,6-dimethyl-1,4-phenylene oxide manufactured by
Aldrich Chemical Co., and
[0107] SBD: styrene-butadiene block copolymer manufactured by
Aldrich Chemical Co.
[0108] Inorganic Fillers:
[0109] (1) SiO.sub.2A: a spherical filler made of silicon dioxide
(average particle size: 7 .mu.m, and dielectric loss tangent at 10
GHz: less than 0.001), and
[0110] (2) SiO.sub.2B: a spherical filler made of silicon dioxide
(average particle size: 20 .mu.m, and dielectric loss tangent at 10
GHz: less than 0.001).
[0111] Curing Catalyst;
[0112] 25B: 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3 perhexyne
25B) manufactured by Nippon Oils and Fats Co., Ltd.
[0113] Flame Retardant;
[0114] 8010: SAYTEX 8010 (a bromine-containing flame retardant
having a dielectric loss tangent at 10 GHz of less than 0.002)
manufactured by Albemarl Corporation.
[0115] Glass Cloth;
[0116] (1) NE cloth: cloth of NE glass (dielectric loss tangent at
10 GHz: less than 0.0036), and
[0117] (2) SiO.sub.2 cloth: glass cloth of silicon dioxide
(dielectric loss tangent at 10 GHz: less than 0.001).
[0118] Copper Foil;
[0119] Rolled copper foil having a thickness of 18 .mu.m and an
average of roughness values at 10 points (Rz) of 1.3 .mu.m.
[0120] Treating Agent;
[0121] KBM 503: .gamma.-methacryloxypropyltrimethoxysilane
(Shin-Etsu Silicone from Shin-Etsu Chemical Co., Ltd.).
[0122] (3) Dielectric Loss Tangent Reduction Treatment of an
Inorganic Filler
[0123] A silicon dioxide filler was added to a solution of KBM 503
in methanol, and the resulting mixture was stirred with a ball mill
for 8 hours. Then, the filler was collected by filtration and dried
at 120.degree. C. for 4 hours. The content of the treating agent
was adjusted to 0.06 wt %, 0.3 wt % or 3.0 wt % based on the weight
of the inorganic filler.
[0124] (4) Preparation Method of a Varnish
[0125] A varnish of a resin composition was prepared by dissolving
predetermined amounts of the high-molecular weight compounds, the
crosslinking component, the curing catalyst and the filler in
chloroform.
[0126] (5) Production of a Resin Plate
[0127] The above-mentioned varnish was applied on a PET film, dried
and then peeled. A predetermined amount of the peeled film was
placed in a spacer made of polytetrafluoro-ethylene and was heated
and pressed in a vacuum through a polyimide film and an end plate
to obtain a resin plate as a cured product. The heating conditions
were 180.degree. C./100 minutes and the pressing pressure was 1.5
MPa. The dimensions of the resin plate were 70 mm.times.70
mm.times.1 mm.
[0128] (6) Dielectric Loss Tangent Reduction Treatment of Glass
Cloth
[0129] Glass cloth was immersed in a 1 wt % solution of KBM 503 in
methanol and allowed to stand for 8 hours. The glass cloth was
taken out of the treating solution and dried at 120.degree. C. for
4 hours to be subjected to dielectric loss tangent reduction
treatment.
[0130] (7) Dielectric Loss Tangent Reduction Treatment of Copper
Foil
[0131] Copper foil was immersed in a 1 wt % solution of KBM 503 in
methanol and allowed to stand for 8 hours. The copper foil was
taken out of the treating solution and dried at room temperature
for 4 hours and then at 1,000.degree. C. under a nitrogen
atmosphere for 1 hour to be subjected to dielectric loss tangent
reduction treatment.
[0132] (8) Production of a Prepreg
[0133] As to all the prepregs produced in Examples, they were
produced by impregnating the predetermined glass cloth with the
resin composition varnish and drying the varnish at room
temperature for about 1 hour and then at 90.degree. C. for 60
minutes.
[0134] (9) Production of a Cured Product of Each Prepreg
[0135] Characteristics of a cured product of each prepreg were
evaluated in order to know the dielectric characteristics of a
laminate sheet and a printed wiring board. Each prepreg produced by
the process described above was heated and pressed in a vacuum to
produce a prepreg cured product. The heating conditions were
180.degree. C./100 minutes and the pressing pressure was 1.5 MPa.
The dimensions of the prepreg cured product were 70 mm.times.70
mm.times.0.1 mm.
[0136] (10) Production of Resin Clad Copper (RCC)
[0137] Resin clad copper was produced by applying the varnish of
Example 10 on copper foil subjected to dielectric loss tangent
reduction treatment, and drying the varnish at room temperature for
about 1 hour and then at 90.degree. C. for 60 minutes. The
thickness of the resin layer was 50 .mu.m.
[0138] (11) Measurement of Permittivity and Dielectric Loss
Tangent
[0139] A value at 10 GHz of each of permittivity and dielectric
loss tangent was measured by a cavity resonance method (a network
analyzer Model 8722ES manufactured by Agilent Technologies, and a
cavity resonator manufactured by Kanto Electronics Application and
Development Inc.).
[0140] (12) Glass Transition Temperature (Tg) and Elastic
Modulus
[0141] Tg was determined with a viscoelasticity measuring apparatus
(DMA) Model DVA-200 manufactured by IT Keisoku Seigyo Co., Ltd. The
dimensions of a sample were 2 mm.times.30 mm.times.0.1 mm, the
distance between supports was 20 mm, and the heating rate was
5.degree. C./minute.
[0142] (13) Flame Retardancy
[0143] Samples for evaluating flame retardancy were obtained by
cutting each of the previously produced resin plate and prepreg
cured product to dimensions of 10 mm.times.70 mm. A test for
flammability was carried out 10 times according to UL-94 standard,
and a sample having an average combustion time of 5 seconds or less
and a maximum combustion time of 10 seconds or less was rated
V0.
[0144] (14) Peel Strength
[0145] Samples for measuring peel strength were produced as
follows. The rough surface of copper foil was attached to each side
of the previously produced prepreg, and the resulting assembly was
heated and pressed in a vacuum through a polyimide film and an end
plate to produce a laminate sheet. The heating conditions were
180.degree. C./100 minutes and the pressing pressure was 4.5 MPa.
The dimensions of the laminate sheet were 70.times.70.times.0.14
mm. The copper foil of the laminate sheet was cut to a width of 10
mm and the peel strength of the resulting piece of the copper foil
was measured.
Comparative Example 1
[0146] Comparative Example 1 is a resin composition containing no
inorganic filler. Table 3 shows the make-up and dielectric
characteristics of the resin composition. The permittivity at 10
GHz was 2.4 and the dielectric loss tangent was 0.002.
1 TABLE 3 Comparative Comparative Comparative Comparative Example 1
Example 2 Example 3 Example 4 BVPE (parts by 50 50 50 50 weight)
PPE (parts by 50 50 50 50 weight) SBD (parts by 5 5 5 5 weight)
SiO.sub.2A (parts 0 50/18 200/45 300/56 by weight/ vol %) 25B
(parts by 0.5 0.5 0.5 0.5 weight) Concentration 0 0 0 0 (wt %) of
the treating agent relative to the filler Concentration 0 0 0 0
(parts by weight) of the treating agent per 100 parts by weight of
the resin composition Permittivity 2.4 2.7 3 3.2 Dielectric loss
0.002 0.002 0.002 0.002 tangent
Comparative Examples 2 to 4
[0147] Comparative Examples 2 to 4 are resin compositions obtained
by adding various amounts of an inorganic filler not subjected to
dielectric loss tangent reduction treatment. Table 3 also shows the
make-ups and dielectric characteristics of these compositions. The
value of the dielectric loss tangent was hardly improved in spite
of the addition of the inorganic filler having a low dielectric
loss tangent.
Examples 1 to 9
[0148] Examples 1 to 9 are resin compositions obtained by adding an
inorganic filler subjected to each of various dielectric loss
tangent reduction treatments. Table 1 shows the make-ups and
characteristics of these compositions. The dielectric loss tangent
of the compositions of Comparative Examples 2 to 4 containing the
inorganic filler not subjected to dielectric loss tangent reduction
treatment was 0.002, while the dielectric loss tangent of the
compositions of Examples 1 to 9 containing the filler subjected to
each dielectric loss tangent reduction treatment was
0.0011.about.0.0017, an improved value. By this fact, it was
confirmed that the dielectric loss tangent is reduced by the
addition of the filler subjected to each dielectric loss tangent
reduction treatment.
2 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example
6 Example 7 Example 8 Example 9 BVPE (parts by 50 50 50 50 50 50 50
50 50 weight) PPE (parts by 50 50 50 50 50 50 50 50 50 weight) SBD
(parts by 5 5 5 5 5 5 5 5 5 weight) SiO.sub.2A (parts by 50/18
100/30 200/45 50/18 100/30 200/45 50/18 100/30 200/45 weight/vol %)
25B (parts by 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 weight)
Concentration 0.06 0.06 0.06 0.3 0.3 0.3 3 3 3 (wt %) of the
treating agent relative to the filler Concentration 0.02 0.03 0.04
0.1 0.15 0.19 0.96 1.46 1.96 (parts by weight) of the treating
agent per 100 parts by weight of the resin composition Permittivity
2.7 2.8 3 2.7 2.8 3 2.7 2.8 3 Dielectric 0.0011 0.0012 0.0014
0.0014 0.0015 0.0016 0.0015 0.0016 0.0017 loss tangent
Examples 10 to 12
[0149] Examples 10 to 12 are resin compositions containing an
inorganic filler subjected to dielectric loss tangent reduction
treatment and a flame retardant 8010 having a low dielectric loss
tangent. Table 2 shows the make-ups and characteristics of these
compositions. It was confirmed that both a high flame retardancy
and a very low dielectric loss tangent can be attained by the
addition of the inorganic filler subjected to dielectric loss
tangent reduction treatment and the employment of the flame
retardant having a low dielectric loss tangent.
3 TABLE 2 Example 10 Example 11 Example 12 BVPE (parts by 50 50 50
weight) PPE (parts by 50 50 50 weight) SBD (parts by 5 5 5 weight)
SiO.sub.2B (parts by 50 100 200 weight/vol %) 25B (parts by 0.5 0.5
0.5 weight) 8010 40 40 40 Concentration 0.06 0.06 0.06 (wt %) of
the treating agent relative to the filler Concentration 0.02 0.02
0.03 (parts by weight) of the treating agent per 100 parts by
weight of the resin composition Permittivity 2.7 2.8 3 Dielectric
0.0011 0.0012 0.0013 loss tangent Flame VO VO VO retardancy
Examples 13 to 16
[0150] Examples 13 to 16 are prepregs obtained by impregnating
glass cloth with the resin composition of Example 10 of the present
invention. The dielectric loss tangent of a cured product of the
prepreg of Example 13 obtained by using NE cloth not subjected to
dielectric loss tangent reduction treatment was 0.002. Thus, it was
confirmed that the dielectric loss tangent of the prepreg cured
product had an increased value owing to the influence of the
dielectric loss tangent of NE cloth.
[0151] On the other hand, the dielectric loss tangent of a cured
product of the prepreg of Example 14 obtained by using NE cloth
subjected to dielectric loss tangent reduction treatment was
0.0016, namely, the increase of the dielectric loss tangent was
suppressed as compared with Example 13. By this fact, it was
confirmed that the dielectric loss tangent reduction treatment of
the glass cloth is effective in reducing the dielectric loss
tangent of the prepreg cured product. The dielectric loss tangent
of a cured product of the prepreg of Example 15 obtained by using
SiO.sub.2 cloth not subjected to dielectric loss tangent reduction
treatment was 0.0011, which was substantially the same as the
dielectric loss tangent of a cured product of the resin composition
of Example 10.
[0152] On the other hand, the dielectric loss tangent of a cured
product of the prepreg of Example 16 obtained by using SiO.sub.2
cloth subjected to dielectric loss tangent reduction treatment was
0.0009, a reduced value. All of the cured products of the prepregs
of Examples 13 to 16 had a good flame retardancy and a high glass
transition temperature of 220.degree. C. Therefore, they are
considered suitable as a component in a multilayer printed wiring
board for high frequency. Table 4 shows the results described
above.
4 TABLE 4 Example Example Example Example 13 14 15 16 Resin
Composition The same as in Example 10 Glass cloth NE Cloth
SiO.sub.2 cloth Dielectric loss tangent No Yes No Yes reduction
treatment Resin content 55 55 55 55 Permittivity 3.1 3.1 3 3
Dielectric loss tangent 0.002 0.0016 0.0011 0.0009 Flame retardancy
VO VO VO VO Glass transition 220 220 220 220 temperature
Examples 17 to 20
[0153] Table 5 shows the peel strength of laminate sheets of
Examples 17 to 20 produced by using each of the prepregs of
Examples 14 and 16 of the present invention and rolled copper foil
having an average of surface roughness values at 10 points of 1.3
.mu.m. The copper foil used in the laminate sheets of Examples 17
and 19 was that not subjected to dielectric loss tangent reduction
treatment, and both of these laminate sheets had a peel strength of
0.4 kN/m. On the other hand, the laminate sheets of Examples 18 and
20, the copper foil of which was that subjected to dielectric loss
tangent reduction treatment, had an improved peel strength of 0.8
kN/m. Thus, it was confirmed that the dielectric loss tangent
reduction treatment of the copper foil is effective in improving
the peel strength.
Table 5
[0154]
5TABLE 5 Example Example Example Example 17 18 19 20 Structure of a
The same as The same as prepreg Example 14 Example 16 Dielectric
loss No Yes No Yes tangent reduction treatment of copper foil Peel
strength 0.4 0.8 0.4 0.8 (kN/m)
Example 21
[0155] FIG. 1 shows an example of the production of a first
multilayer printed wiring board of the present invention.
[0156] (A) A photoresist (HS 425, mfd. by Hitachi Chemical Co.,
Ltd.) was laminated on one side of the double-wall copper-clad
laminate sheet obtained in Example 20, and the whole surface of the
photoresist was exposed to light. Then, a photoresist (HS 425, mfd.
by Hitachi Chemical Co., Ltd.) was laminated on the other copper
surface and exposed to light according to a test pattern, and the
unexposed portion of the photoresist was developed with a 1% sodium
carbonate solution.
[0157] (B) The exposed portion of the copper foil was removed by
etching with an etching solution containing 5% sulfuric acid and 5%
hydrogen peroxide, to form conductor wiring on one side of the
double-wall copper-clad laminate sheet.
[0158] (C) The residual photoresist was removed with a 3% sodium
hydroxide solution to obtain a wiring board having the wiring on
one side. Two wiring board were produced in the same manner as
above.
[0159] (D) The prepreg of Example 16 was held between the wiring
sides of the two wiring boards and the resulting assembly was
heated and pressed in a vacuum to form a multilayer structure. The
heating conditions were 180.degree. C./100 minutes and the pressing
pressure was 4 MPa.
[0160] (E) A photoresist (HS 425, mfd. by Hitachi Chemical Co.,
Ltd.) was laminated on the outer layer copper on each side of the
produced multilayer board and exposed to light according to a test
pattern, and the unexposed portion of the photoresist was developed
with a 1% sodium carbonate solution.
[0161] (F) The exposed portion of the copper foil was removed by
etching with an etching solution containing 5% sulfuric acid and 5%
hydrogen peroxide, and the residual photoresist was removed with a
3% sodium hydroxide solution to form outer layer wirings.
[0162] (G) A through-hole for connecting the inner layer wirings
and the outer layer wirings was formed by drilling.
[0163] (H) The wiring board thus obtained was immersed in a
colloidal solution of a plating catalyst to place the catalyst in
the through-hole and on the board surface.
[0164] (I) After the activation of the plating catalyst, seed films
of about 1 .mu.m were formed by electroless plating (CUST 2000,
mfd. by Hitachi Chemical Co., Ltd.).
[0165] (J) A photoresist (HN 920, mfd. by Hitachi Chemical Co.,
Ltd.) was laminated on each side of the wiring board.
[0166] (K) The through-hole portion and the edges of the wiring
board were masked and the wiring board was exposed to light,
followed by development with 3% sodium carbonate. Thus, openings
were formed.
[0167] (L) Electrodes were set at the edges of the wiring board and
a plated copper film was formed in a thickness of about 18 .mu.m on
the through portion by electroplating.
[0168] (M) The electrode portions were cut off and the residual
photoresist was removed with a 5% aqueous sodium hydroxide
solution.
[0169] (N) The wiring board was immersed in an etching solution
containing 5% sulfuric acid and 5% hydrogen peroxide, to conduct
etching to a thickness of about 1 .mu.m, to remove the seed films.
Thus, the multilayer wiring board was produced.
[0170] In the case of this multilayer wiring board, disconnection
of the wiring or peeling of the wiring was not caused in the
formation of the multilayer structure. In addition, when the
multilayer wiring board was held in a reflow bath of molten solder
at 200.degree. C. for 10 minutes and then in a bath of molten
solder at 288.degree. C. for 2 minutes, peeling of the resin
boundary surface or the wiring, or the like was not caused.
Example 22
[0171] FIG. 2 shows an example of the production of a second
multilayer printed wiring board of the present invention.
[0172] (A) A photoresist (HS 425, mfd. by Hitachi Chemical Co.,
Ltd.) was laminated on each side of the double-wall copper-clad
laminate sheet obtained in Example 20, and then was exposed to
light according to a test pattern, and the unexposed portion of the
photoresist was developed with a 1% sodium carbonate solution.
[0173] (B) The exposed portion of the copper foil was removed by
etching with an etching solution containing 5% sulfuric acid and 5%
hydrogen peroxide, to form conductor wiring on each side of the
laminate sheet.
[0174] (C) The residual photoresist was removed with a 3% sodium
hydroxide solution to obtain a wiring board having the wiring on
each side.
[0175] (D) The wiring board was held between two sheets of RCC
having on the surface a resin layer made of the composition of
Example 10, and the resulting assembly was heated and pressed in a
vacuum to form a multilayer structure. The heating conditions were
180.degree. C./100 minutes and the pressing pressure was 4 MPa.
[0176] (E) A photoresist (HS 425, mfd. by Hitachi Chemical Co.,
Ltd.) was laminated on the outer layer copper on each side of the
produced multilayer board and exposed to light according to a test
pattern, and the unexposed portion of the photoresist was developed
with a 1% sodium carbonate solution.
[0177] (F) The exposed portion of the copper foil was removed by
etching with an etching solution containing 5% sulfuric acid and 5%
hydrogen peroxide, and the residual photoresist was removed with a
3% sodium hydroxide solution to form the outer layer wirings.
[0178] (G) A through-hole for connecting the inner layer wirings
and the outer layer wirings was formed by drilling.
[0179] (H) The wiring board thus obtained was immersed in a
colloidal solution of a plating catalyst to place the catalyst in
the through-hole and on the board surface.
[0180] (I) After the activation of the plating catalyst, seed films
of about 1 .mu.m were formed by electroless plating (CUST 2000,
mfd. by Hitachi Chemical Co., Ltd.).
[0181] (J) A photoresist (HN 920, mfd. by Hitachi Chemical Co.,
Ltd.) was laminated on each side of the wiring board.
[0182] (K) The through-hole portion and the edges of the wiring
board were masked and the wiring board was exposed to light,
followed by development with 3% sodium carbonate. Thus, openings
were formed.
[0183] (L) Electrodes were set at the edges of the wiring board and
a plated copper film was formed in a thickness of about 18 .mu.m on
the through portion by electroplating.
[0184] (M) The electrode portions were cut off and the residual
photoresist was removed with a 5% aqueous sodium hydroxide
solution.
[0185] (N) The wiring board was immersed in an etching solution
containing 5% sulfuric acid and 5% hydrogen peroxide, to conduct
etching to a thickness of about 1 .mu.m, to remove the seed films.
Thus, the multilayer wiring board was produced.
[0186] In the case of this multilayer wiring board, disconnection
of the wiring or peeling of the wiring was not caused in the
formation of the multilayer structure. In addition, when the
multilayer wiring board was held in a reflow bath of molten solder
at 200.degree. C. for 10 minutes and then in a bath of molten
solder at 288.degree. C. for 2 minutes, peeling of the resin
boundary surface or the wiring, or the like was not caused.
Example 23
[0187] This example is a case where an inorganic filler was treated
with a treating agent unreactive to the polyfunctional styrene
compound, i.e., a compound of the above-mentioned group (2).
[0188] The inorganic filler SiO.sub.2 (A) was previously treated
with 0.3 wt % mercaptotrimethoxysilane. The thus treated inorganic
filler was added to the resin composition of Example 1 in an amount
of 50 wt %, and a resin plate was molded by the predetermined
method. The permittivity at 10 GHz of the obtained resin plate was
2.8% and its dielectric loss tangent was 0.0015. Since the
dielectric loss tangent was lower than that of the composition of
Comparative Example 1, it was confirmed that the treating agent
unreactive to styrene group is also effective in reducing the
dielectric loss tangent of the cured product.
Examples 24 to 27
[0189] In these examples, the dielectric loss tangent of cured
products of resin compositions containing various flame retardants,
respectively, was measured. The flame retardants A, B, C and D
added are the same compounds as described above. Table 6 shows the
make-ups of the resin compositions and the permittivity and
dielectric loss tangent of the cured products.
6 TABLE 6 Example 24 Example 25 Example 26 Example 27 BVPE (parts
by 50 50 50 50 weight) PPE (parts by 50 50 50 50 weight) SBD (parts
by 5 5 5 5 weight) 25B (parts by 0.5 0.5 0.5 0.5 weight) Flame
retardant A -- -- 40 -- Flame retardant B -- -- -- 40 Flame
retardant C 40 -- -- -- Frame retardant D -- 40 -- -- Permittivity
2.5 2.5 2.5 2.6 Dielectric loss 0.0016 0.0017 0.0017 0.0018
tangent
[0190] The resin composition of the present invention is suitable
as an insulating material for electrical parts for high frequency
and can be used in a wiring board for high-frequency signal and a
prepreg used in the wiring board. In addition, according to the
present invention, the dielectric loss tangent of a prepreg
composed of a composite of the resin composition and glass cloth or
glass nonwoven fabric can be markedly reduced and moreover, the
peel strength between the prepreg and conductor foil having a low
surface roughness can be increased. Accordingly, a multilayer
printed wiring board excellent in both high-frequency
characteristics and reliability can be obtained.
[0191] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *